Gene For Left-handedness Identified in ScienceDaily. The original paper is LRRTM1 on chromosome 2p12 is a maternally suppressed gene that is associated paternally with handedness and schizophrenia:
Left-right asymmetrical brain function underlies much of human cognition, behavior and emotion. Abnormalities of cerebral asymmetry are associated with schizophrenia and other neuropsychiatric disorders. The molecular, developmental and evolutionary origins of human brain asymmetry are unknown. We found significant association of a haplotype upstream of the gene LRRTM1...with a quantitative measure of human handedness in a set of dyslexic siblings, when the haplotype was inherited paternally...While we were unable to find this effect in an epidemiological set of twin-based sibships, we did find that the same haplotype is overtransmitted paternally to individuals with schizophrenia/schizoaffective disorder...We then found direct confirmatory evidence that LRRTM1 is an imprinted gene in humans that shows a variable pattern of maternal downregulation. We also showed that LRRTM1 is expressed during the development of specific forebrain structures, and thus could influence neuronal differentiation and connectivity. This is the first potential genetic influence on human handedness to be identified, and the first putative genetic effect on variability in human brain asymmetry. LRRTM1 is a candidate gene for involvement in several common neurodevelopmental disorders, and may have played a role in human cognitive and behavioral evolution.
The paper seems to be alluding to a lot of separate and distinct facts which need to be glued together into a plausible causal system. In other words, more work needs to be done. Nevertheless, multiple genetic issues are highlighted, genomic imprinting, behavioral differences and evolutionary changes in the human lineage in regards to neurological organization. It shows how many different things may hinge on one genetic point of difference because of the interconnected nature of gene expression and development.